Effects of Intrinsic Flexibility on Adsorption Properties of Metal-Organic Frameworks at Dilute and Nondilute Loadings
Effects of Intrinsic Flexibility on Adsorption Properties of Metal-Organic Frameworks at Dilute and Nondilute Loadings
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DOI：
10.1021/acsami.9b10622
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发表时间：
2019-08-28
影响因子：
9.5
通讯作者：
Sholl, David S.
中科院分区：
文献类型：
--
作者：
Agrawal, Mayank;Sholl, David S.
纳米多孔材料中吸附的分子模拟已经成为对这些材料的实验研究的宝贵补充。在几乎所有的情况下，这些模拟都将吸附材料视为刚性的。我们使用分子模拟来检验这种近似在金属有机骨架(MOF)中吸附的有效性，这些MOF具有骨架柔性而不会因为热振动而改变其晶胞。所有的纳米多孔材料都受到这种骨架灵活性的影响。我们考察了9种分子(CO2、CH4、乙烷、乙烯、丙烷、丙烯、丁烷、Xe和Kr)和4种分子混合物(CO2/CH4、乙烷/乙烯、丙烷/丙烯/丁烷和Xe/Kr)在100种MOF中的稀吸和非稀吸附条件。结果表明，在非稀释条件下，骨架柔性对单组分吸附量的影响很小，但在稀释和非稀释条件下的吸附选择性都会受到柔性的显著影响。骨架柔性对吸附的影响最大的是在稀疏吸附极限下的吸附。这些结果表明，在试图对MOF和类似材料的吸附选择性进行定量预测时，考虑框架灵活性的重要性在过去可能被低估了。
Molecular simulation of adsorption in nanoporous materials has become a valuable complement to experimental studies of these materials. In almost all cases, these simulations treat the adsorbing material as rigid. We use molecular simulations to examine the validity of this approximation for the adsorption in metal-organic frameworks (MOFs) that have framework flexibility without change in their unit cells because of thermal vibrations. All nanoporous materials are subject to this kind of framework flexibility. We examine the adsorption of nine molecules (CO2, CH4, ethane, ethene, propane, propene, butane, Xe, and Kr) and four molecular mixtures (CO2/CH4, ethane/ethene, propane/propene/butane, and Xe/Kr) in 100 MOFs at dilute and nondilute adsorption conditions. Our results show that single-component adsorption uptakes at nondilute conditions are only weakly affected by framework flexibility, but adsorption selectivities at both dilute and nondilute conditions can be significantly affected by flexibility. The most dramatic impacts of framework flexibility occur for adsorption uptake in the limit of dilute adsorption. These results suggest that the importance of including framework flexibility when attempting to make quantitative predictions of adsorption selectivity in MOFs and similar materials may have been underestimated in the past.